Whether we are focused on our smartphones, reading a book, or engaging with someone at a table, the things we concentrate on are never alone; there are always additional objects or people around us. However, the impact of this visual ‘clutter’ on how our brain processes what we see is not yet fully understood. Recent research indicates that such clutter changes the way information travels within the brain, depending significantly on where that clutter is located in our broader visual field. These insights enhance our comprehension of perception’s neural foundations and provide a richer understanding of the brain’s visual cortex.
Whether we are focused on our smartphones, reading a book, or engaging with someone at a table, the things we concentrate on are never alone; there are always additional objects or people around us. However, the impact of this visual “clutter” on how our brain processes what we see is not yet fully understood.
A recent study published in the journal Neuron by Yale researchers demonstrates that this clutter affects the flow of information in the brain, influenced by the specific location of that clutter in our visual range. These findings advance our understanding of the neural mechanisms behind perception and the visual cortex’s functions.
“Previous studies have indicated that visual clutter influences how we perceive things, depending on its position relative to what we are looking at,” explained Anirvan Nandy, an assistant professor of neuroscience at Yale School of Medicine (YSM) and a co-senior author of the study. “For example, if I’m trying to read the word ‘cat’ from the side of my vision, the letter ‘t’ will have a more significant impact on my ability to identify the letter ‘a’ than the letter ‘c,’ even though both are equidistant from ‘a.'”
This effect is termed “visual crowding,” and it explains why we struggle to read things off to the side, irrespective of our efforts, and why identifying objects becomes challenging amidst the clutter in our peripheral vision, according to Nandy.
In this study, the researchers aimed to uncover what occurs in the brain when visual clutter is present.
To achieve this, they trained macaque monkeys—whose visual capabilities closely resemble those of humans—to focus on the center of a screen while different visual stimuli were presented both in and outside of their receptive fields. They monitored neural activity in the primary visual cortex, which processes visual information in the brain.
The findings revealed that the exact position of the clutter within the monkeys’ visual fields only slightly influenced the way information transferred between neurons in the primary visual cortex. However, it did impact the efficiency of that information flow.
This can be likened to a phone tree, where each person calls another to relay information until everyone in the group has been informed. In terms of visual perception, the clutter’s location may not change the sequence of relaying information, but it does affect how effectively the message is communicated from one person to the next.
“For instance, clutter in one area may drive the information in a certain layer of the primary visual cortex less than clutter in another area,” commented Monika Jadi, an assistant professor of psychiatry at YSM and a co-senior author of the study.
Additionally, the researchers discovered a general characteristic of the visual cortex that was not previously acknowledged.
There are multiple brain regions that play a role in seeing and recognizing objects, and information is transmitted through these areas in a specific sequence. For example, the primary visual cortex forwards information packets to the secondary visual cortex, which subsequently passes on its information to the next area.
“It was already known that complex calculations occur within individual visual areas, and the results of these calculations get passed on to the next area to complete the object recognition process,” said Jadi.
What the new study highlighted was that within these larger areas, smaller subunits are performing separate computations and relaying only some of that information to other subunits. This discovery connects a gap that had previously existed among different disciplines studying visual processing, as mentioned by Nandy.
The research team is now keen to investigate how clutter influences information processing across different brain regions and the role of attention in this system.
“For example, while driving, you might be concentrating on the car in front of you, but your attention could be diverted to a vehicle in another lane as you gauge whether it will merge,” noted Nandy.
This means that while the detailed visual input comes from the car immediately ahead, your focus is directed elsewhere.
“How does that attention account for the fact that even when the clarity of the information isn’t optimal, you can still perceive the attended part of your visual space better than what you are directly looking at?” inquired Jadi. “We aim to delve into how attention impacts information flow in the cortex.”
